1. Field of the Invention
The present invention relates to a method of supporting a board which is made of a ceramic or other fragile material, for mounting an electric component onto the fragile board, for applying an adhesive into a desired spot of the fragile board, or for other purpose. The invention also relates to a device suitable for carrying out such a supporting method.
2. Discussion of Related Art
There is known an operation for manufacturing an electric or electronic circuit, by mounting electric or electronic components onto a circuit board such as a printed circuit board. Such a manufacturing operation is commonly carried out by using a board work system including (a) a board holding device for holding the circuit board, (b) a working head for achieving a predetermined operation in a desired portion of the circuit board held by the board holding device, and (c) a relative movement device for moving the board holding device and the working head relative to each other. As such a board work system, there is known an adhesive applying system and an electric-component mounting system, for example. In the adhesive applying system, the working head takes the form of an applying head for applying an adhesive to the circuit board. In the electric-component mounting system, the working head takes the form of a mounting head for mounting head the electric component onto the circuit board.
In the board working system, it is common that the circuit board is held at a central or non-peripheral portion of its lower surface by a plurality of supporting members of the board holding device. However, it is not easy to support the circuit board in an appropriate manner, particularly, where the circuit board is made principally of a ceramic material which is inherently brittle or fragile and is accordingly easy to be broken or fractured due to its poor elastic deformability if a large stress or force is applied to the circuit board. A metallic material is conventionally used for forming the supporting members. The circuit board is held by the metallic supporting members at its supported surface (one of its opposite surfaces), so that its work surface (the other of its opposite surfaces) is subjected to the predetermined operation while the circuit board is being supported at its supported surface by the supporting members. This manner for supporting the circuit board is effective for maintaining a horizontal posture of the circuit board without the work surface being inclined with respect to the horizontal direction, but is not effective to prevent vibration of the circuit board which is likely to be caused due to shock acting on the circuit board, for example, upon mounting of the electric component onto the circuit board, upon initiation of movement of the circuit board in a direction parallel to its support or work surface, or upon positioning the circuit board in a desired position after the movement. If the vibration of the circuit board is not settled or stopped by the point of time of the mounting of the electric component onto the circuit board, the electric component could not be accurately positioned relative to the circuit board, thereby making it difficult to mount the electric component in a desired portion of the circuit board with high accuracy.
It is considered possible, for example, to replace the metallic supporting member with a supporting member made of a rubber, sponge or other material capable of absorbing the vibration. However, where the circuit board is slightly convexed in the downward direction (i.e., in a direction away from the work surface toward the supported surface), such a downwardly convexed circuit board could not be sufficiently flattened by the supporting member made of the considerably soft material. Further, where the circuit board is slightly convexed in the upward direction (i.e., in a direction away from the supported surface toward the work surface), the circuit board could not be firmly supported at its supported surface by the metallic supporting member in the above-described manner. A supporting member having a suction cup or surface is widely used for supporting such a upwardly convexed circuit board with application of a vacuum pressure to the supported surface through the suction surface. However, if the circuit board made of a ceramic material is considerably deformed by the application of the vacuum pressure, there caused a risk of fracture of the circuit board. These problems are encountered not only where the circuit board is made of a ceramic material but also where the circuit board is made of other fragile material such as a glass material.